This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Mucosal vaccination for HIV/AIDS would provide a preventative solution to the pandemic. Here, we examine the effectiveness of tonsillar application of aldrithiol 2 (AT-2) inactivated SIVmac239, in combination with the B cell and plasmacytoid dendritic cell (PDC) stimulus CpG-C immunostimulatory olinucleotides (CpG-C ISS-ODNs) as the adjuvant. In vitro CpG-C ISS-ODN activation of B cells and PDCs and AT-2 SIV activation of PDCs were not affected by the ubiquitous oral pathogen Candida albicans;elevated CD80 and CD86 expression and several cytokines and chemokines, in particular Th1-attracting factors. To test if CpG-C ISS-ODNs would enhance the effect of a mucosally applied vaccine by activating local PDCs and B cells to augment immunity, macaques had CpG-C ISS-ODNs or control ODNs applied with AT-2 SIV to the tonsillar tissues. Animals received 5 vaccinations every 6 weeks before being challenged rectally with pathogenic SIVmac239, 8 weeks after the last immunization. Although no T or B cell responses were detected prior to challenge, immunization with AT-2 SIV significantly (p0.03) reduced the frequency of infection compared to non-immunized controls, even after additional challenges of the immunized animals. However, there was no beneficial effect of the CpG-C ISS-ODN treatment above the control ODNs. SIV-specific T cell and antibody responses were detected once animals became infected. This work provides the first evidence for AT-2 SIV as a promising vaccine antigen when applied to the oral mucosal-associated lymphoid tissues and has important implications for the advancement of nasopharyngeal vaccination against HIV.